The present invention relates to a HALT/HASS fixturing table for generating secondary vibration using moving balls and multi-axes rails. More particularly, the present invention relates to a HALT/HASS fixturing table mounted on a device for generating primary vibration to generate multi-axes complex waves in 6 degrees of freedom, so that HALT/HASS test (HALT: High Accelerated Life test and HASS: High Accelerated Stress Screening) can be conducted more efficiently and can be conducted with conventional devices for generating vibration.
Generally, prior to mass production of goods provided to consumers, a reliability test is conducted to check the quality and performance of the goods in order to reduce inferior goods and to assure the high quality and reliability of the products.
The reliability test is divided into a climatic reliability test and a mechanical reliability test. The climatic reliability test is to check the influence of environmental conditions such as temperatures, humidity and atmosphere on products, and the mechanical reliability test is to check the influence of conditions such as vibration, shock, impact and collision on products.
Recently, such environmental conditions have become more severe, accelerated and varied to improve failure margin and improve incompleteness of products. The HALT/HASS test is one of the recently developed mechanical reliability tests which have been put to practical use in advanced countries.
In the meantime, vibrational reliability test commonly conducted comprises the steps of: placing a test product on a vibration generator; generating vibration of a certain frequency (e.g., shortened frequency of sine wave, shortened frequency range of random wave and shock wave) by the vibration generator; and observing vibration characteristics of the test product in the certain frequency to check on which point of vibration, i.e., on which resonance point the test product is destroyed.
As mentioned above, conventional vibrational reliability test is to measure the vibration point on which a test product is destroyed by generating a certain frequency of unidirectional wave such as sine wave, shortened frequency range of random wave or shock wave. On the other hand, the HALT/HASS test is to measure the reliability of a test product by using wide frequency range of repetitive shock vibration and simultaneous multi-axes complex waves of 6 degrees of freedom in order to measure failure margin of the product.
However, a repetitive shock vibration table in 6 degrees of freedom which has been used in the conventional HALT/HASS test method used a pneumatic vibration mechanism which is composed of pneumatic cylinders and a rigid aluminum or magnesium table (see FIG. 8). In case of using this conventional pneumatic vibration mechanism, since the vibration spectrum was fixed by the pneumatic vibration cylinders and the structural design of the table, it was not easy for the conventional HALT/HASS test to adapt itself to various test specimens. Also, since an effect of causing acceleration deteriorates due to the fixed vibration spectrum and the lowered maximum vibration level in the low frequency zone, the conventional HALT/HASS test was not effective.
Effective frequency zone in the HALT/HASS test depends on the mass of a test specimen and structural conditions of the fixed vibration spectrum of pneumatic vibration mechanism.
That is, as vibration spectrum in relatively low frequency zone is effective for massive and complex test specimen, and vibration spectrum in high frequency zone is effective for lightweight and simple test specimen, the HALT/HASS test with the fixed vibration spectrum of pneumatic vibration mechanism has difficulties in conducting an effective test for the variety of test specimens.
Further, a device for generating unidirectional vibration used in the conventional reliability test (refer to FIGS. 9, 10 and 11) cannot generate multi-axes vibration waves of 6 degrees of freedom, and thus an auxiliary fixturing table which can easily generate vibration waves of 6 degrees of freedom for the HALT/HASS test has been required.
The object of the present invention is to provide a HALT/HASS fixturing table for generating secondary vibration using moving balls and multi-axes rails, wherein the table is constructed to generate multi-axes complex shock vibration waves of 6 degrees of freedom and mounted on a conventional vibration table for the HALT/HASS test, in order to adapt itself to an optimum vibration spectrum according to the changes of test specimens and various conditions and to enhance the maximum vibration level in the low frequency zone. The HALT/HASS test according to the present invention is conducted more effectively with smooth and flat vibration level in a high frequency zone.
Another object of the present invention is to provide a HALT/HASS fixturing table for generating secondary vibration using moving balls and multi-axes rails, wherein the table is installed on the conventional device for generating unidirectional vibration used in the conventional reliability test to generate secondary vibration, preferably random vibration waves in 6 degrees of freedom, so that the HALT/HASS test can be conducted more easily.
These and other objects of the present invention can be achieved by a HALT/HASS fixturing table for generating secondary vibration using moving balls and multi-axes rails comprising:
a lower panel placed on either a device for generating primary vibration or a fixturing table for use with the device for generating primary vibration, and having on the top surface thereof a plurality of horizontal rails and vertical rails formed in the shape of grooves of a certain depth;
moving balls inserted in the horizontal rails and the vertical rails of the lower panel to move in the horizontal and the vertical rails according to the vibration generated by the device for generating primary vibration;
a buffering member placed on the lower panel to absorb a part of the impact caused by movement of the moving balls and to diffuse the vibration; and
a upper panel placed on the buffering member and fixed to the lower panel by joint means, a specimen for the HALT/HASS test being attached to the upper panel.
If vibration is generated by the device for generating primary vibration, the vibration is delivered to the lower panel, and the moving balls inserted in the horizontal and vertical rails of the lower panel move, thus generating secondary multiple impacts between the upper panel and the lower panel.